(Portland, OR)  --  The power is back on for hundreds of Pacific Power customers after a small tornado knocked out electricity and overturned trailers in North Portland.  The National Weather Service says the EF-O rated twister touched down briefly yesterday afternoon with wind speeds of between 65 and 85 miles per hour.  The tornado overturned three unoccupied semi-truck trailers and broke tree limbs while knocking out the power for more than 800 homes and businesses.